Every PCB design is a delicate balance between functionality and price. In this article, we’ll focus on how to design your board to cost less while still working as intended. In case you missed the first part of this article, feel free to read Part 1 and return here after.

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While in Part 1 we focused mostly on how to save on assembly costs, in this part, we home in on the PCB itself. When it comes to PCB fabrication, the general rule of thumb is the smaller anything is, the more it costs to produce. Now, I’m not talking about the PCB dimensions; I’m talking about the elements that make up the design like vias, trace width/gap, drill size, etc. Another rule of thumb is anything that takes longer to produce, costs more. Simple right? In the sections below, we delve into money-saving tips that follow these two principles.

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Stay within these specs

Remember, the smaller the elements on your board, the more they cost to make. We regularly handle more complex board designs than these, but unless it's necessary, we recommend that you stay within the following specs in order to keep your costs low and reliability high:

• Hole Diameter > 0.25 mm
• Annular Ring > 0.1 mm
• Track and gap width > 0.15 mm
• Board thickness = 0.8 mm, 1.0 mm, 1.20 mm, 1.60 mm, or 2.40 mm
• Number of layers < 8 layers

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Keep your board rectangular

A simple tip is to try keeping your boards rectangular. By doing this, you allow the PCB fabrication process to use a v-scoring technique rather than routing. Routing takes longer to complete compared to v-scoring. Again, anything that saves time also saves money.

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Use a standard board thickness

By using a standard thickness, you allow the fabricator to use readily available stock materials. This reduces your cost and lead time. Standard thicknesses are 0.8mm, 1.0mm, 1.20mm 1.60mm, and 2.40mm.

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Via tenting, plugging, and filling

When it comes to via design considerations, there are three main categories: tenting, plugging, and filling.

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Let’s start with the least expensive option. Tenting a via simply involves covering the via and annular ring with soldermask. This option does not cost anything extra to manufacture since you’re already applying soldermask to your boards. All you need to do, as a designer, is remove the mask clearances from your vias.

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Next up are via plugging and filling. We’ll put these in the same category as they follow the same logic. Both add additional steps to the manufacturing process by requiring extra machinery to actually plug/fill the vias. This adds cost and lead time to your boards. Therefore, if your design doesn’t require 100% assurance that your vias are filled, go with tenting as it adds some protection without the additional cost.

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Via-In-Pad: useful yet expensive

Via-in-pad allows engineers to design with fine-pitch BGA parts while easing the routing process. But as always, there’s a drawback...they’re expensive. If you’re trying to cut down on manufacturing costs, consider using a different part package that doesn’t require via-in-pad. The via-in-pad process requires a few extra steps in the manufacturing process that contribute to the higher cost. Below are the (simplified) steps to create a via-in-pad. By avoiding these steps with a different part package, you save on manufacturing costs.

1. A hole for the via is drilled (typically with a laser drill)
2. The hole is plated
3. The hole is filled with resin, conductive material, or soldermask
4. The hole is plated again

Pro Tip: If your design requires at least one via-in-pad, it doesn’t add much cost to have other components with via-in-pad as well. The first one is always the most expensive to add.

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Microvias, blind vias, and buried vias

A microvia (as the name suggests) is a very small via. Typically, a microvia is defined as a via with a hole less than 0.15 mm. To achieve a hole this small, a laser is most often used. Adding the laser drilling process adds more cost to your boards. Since blind and buried vias generally use the same laser drilling process, they also contribute to a higher manufacturing cost. Therefore, if your design doesn’t require laser drilling, you’ll have designed a lower cost board.

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Hard gold finish and gold fingers

If you’re looking to cut down on costs, avoid anything with the word “gold” in it. As one would expect, a hard gold finish adds extra material cost but also additional labor costs. Hard gold is typically applied to a gold finger edge connector. By adding additional material cost and labor for manufacturing the gold fingers, you’re contributing to a higher manufacturing cost. As with many of the sections above, if your design doesn’t need hard gold or gold fingers, don’t use them. If it does, make sure to specify them on the board tab of your CircuitHub project.

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Castellated edges

A castellated edge has a unique manufacturing process that adds lead time and cost. To create a castellated edge, a routing process must be added to first cut off half the holes on the edge of the board. From there, the half-holes are plated. This additional process adds to your board's costs.

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Understanding which parts of a PCB contribute to their manufacturing costs can help you think about your next design in a different way. So next time you’re designing a board, think of each step that goes into your board design and the process behind it!

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